The invention relates to a method and a device for monitoring the bogies of multiple-axle vehicles. The method is applicable to vehicles which are guided on a roadway or on rails. The system includes acceleration sensors for converting vibrations of a monitored object into signals that are subsequently evaluated by a signal processing unit.
In rail traffic, defective elements of the bogies of train cars represent a hazard. Defects can develop owing to material wear during driving or insufficient maintenance. Because of the increased speeds on many stretches, the risk of accidents caused by defective axle bearings and brakes is growing.
In order to prevent accidents, it is desirable to detect abnormal operating conditions early, in order to be able to initiate corresponding safety measures (e.g. a reduction of driving speed) immediately.
The publication Signal+Draht [signal and wire], Tetzlaff Verlag Hamburg, January/February 1999, pages 30-33, describes a system wherein infrared sensors a placed along a track for sensing so-called hot boxes. When taking the measurement, it must be taken into consideration that the ambient temperature and sunshine can vary over a wide range, and that the monitored parts are usually covered with a layer of dirt. Furthermore, the axle bearings often have different operating temperatures, to which the measuring device must be adapted. In addition, the temperature measurement can only detect defects which cause heating of the monitored parts of the bogie.
It is therefore expedient to utilize a monitoring device which detects impermissible deviations not of thermal operating behavior, but rather of mechanical operating behavior, to which the measuring device expediently adapts.
U.S. Pat. No. 5,419,197 describes a device for detecting impermissible deviations of the mechanical operating behavior of a monitored object. That device includes an acceleration sensor which is mounted at the monitored object and which converts the vibrations of the subject into acceleration signals, which are processed in a signal processor and a neural network in order to detect impermissibly deviating operating behavior.
Using that type of monitoring device, it would also be possible to detect impermissible deviations of the mechanical operating behavior of a bogie on which an acceleration sensor is mounted. Since a bogie is not led on an ideal roadway, i.e. ideal rails, the mechanical operating behavior of the bogie is influenced not only by changes occurring within the bogie but also by feedback from the road or track. The danger therefore exists that feedback of the roadway or rails will cause misinterpretation of the mechanical operating behavior of the bogie, potentially triggering false error messages.
It is accordingly an object of the invention to provide a method and device for monitoring the bogies of multi-axle vehicles, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows deviations of changes in the mechanical operating behavior of the bogies to be measured independently of external influences.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of monitoring a bogie of a multi-axle vehicle guided on a running surface, such as a roadway or rails. The method comprises the following steps:
detecting respective accelerations of at least two axles of the bogie with acceleration sensors;
subjecting sensor signals received from the acceleration sensors to a Fourier transformation in FFT modules provided in an adaptation stage and generating frequency profiles with the FFT modules;
selecting one or more comparison operations from the following group:
comparing the frequency profiles, in a first check module, to one another, to originally measured frequency profiles, and/or to a correspondingly selected standard profile;
comparing the frequency profiles, in a second check module, to respective average value profiles formed in storage stages; and
comparing the average value profiles formed in storage stages directly to each other, to originally measured frequency profiles, and/or to a correspondingly selected standard profile; and
comparing determined deviations to threshold values, and accordingly delivering message signals to systems serving to control the vehicle.
In an alternative method according to the invention, the following steps are required:
detecting respective accelerations of at least two axles of the bogie with acceleration sensors;
shifting sensor signals received from the acceleration sensors relative to one another with a controllable timing element, to compensate for a time difference between instants at which the wheels of the bogie respectively pass a given point on the running surface;
subtracting the shifted signal curves from one another in a difference stage to form a resulting signal curve sres=s11axe2x88x92*s11b representing a condition of the bogie; and
comparing the resulting signal curve to at least one threshold value or threshold value profile in a signal processing unit.
In accordance with an added feature of the invention, the time difference between the instants is calculated by correlating the sensor signals (s11axe2x88x92s11b and s11axe2x88x92*s11b), or from a velocity of the vehicle and a spacing between the axles carrying the respective wheels.
In accordance with another feature of the invention, there is provided a first threshold value or threshold value profile, and it is determined therewith, by comparison with the signal curve, whether vibrations are being caused by the running surface or by an anomaly of the bogie; and/or providing a second threshold value or threshold value profile, and determining therewith whether the bogie contains a defect that should be signaled.
In accordance with a further feature of the invention, the deviations determined in the first check module and/or the second check module are registered as defects of the bogie or the running surface in dependence on a result of an evaluation of the signal curve sres=s11axe2x88x92*s11b, where s11a is a sensor signal and *s11b is the delayed sensor signal.
In accordance with again an added feature of the invention, one of the threshold values and the threshold value profiles is modified, selected as a function of frequency, in dependence on one of a velocity and an acceleration of the vehicle.
In accordance with again an additional feature of the invention, the disturbances detected in dependence on the deviations are linked to time and/or location information.
In accordance with a further feature of the invention, there is determined, in the signal processing unit, a period duration of periodically occurring disturbances, and a velocity of the vehicle is calculated as a function of a diameter of the wheels.
With the above and other objects in view there is also provided, in accordance with the invention, a device for monitoring a bogie of a multi-axle vehicle guided on a running surface such as rails or a road, comprising:
a plurality of acceleration sensors respectively disposed for sensing vibrations of at least two axles of the bogie and configured to convert vibrations of the axles into sensor signals;
a signal processing unit connected to the sensors for receiving the sensor signals for further evaluation; an adaptation stage having at least one FFT module connected to receive the sensor signals from the acceleration sensors and for outputting frequency profiles;
at least one comparison unit selected from the group of units consisting of:
a first check module configured for one of comparing the frequency profiles to one another, comparing the frequency profiles to originally measured frequency profiles, and comparing the frequency profiles to a correspondingly selected standard profile;
storage stages, and a second check module configured to compare the frequency profiles to respective average value profiles formed in the storage stages; and
a comparator for comparing the average value profiles formed in the storage stages directly to each other, to originally measured frequency profiles, or to a correspondingly selected standard profile; and
a device for comparing the determined deviations with threshold values, and for delivering messages accordingly to systems serving to control the vehicle.
Alternatively, the device for monitoring a bogie of a multi-axle vehicle guided on a running surface comprises:
a plurality of acceleration sensors respectively disposed for sensing vibrations of at least two axles of the bogie and configured to convert vibrations of the axles into sensor signals;
a controllable timing element connected to receive the sensor signals for shifting the sensor signals relative to one another to compensate for a time difference between instants at which the wheels of the bogie respectively pass a given point on the running surface;
a difference stage for subtracting the shifted signal curves from one another to form a resulting signal curve sres=s11axe2x88x92*s11b representing a condition of the bogie; and
a signal processing unit for comparing the resulting signal curve sres=s11axe2x88x92*s11b to at least one threshold value or threshold value profile.
The inventive method makes it possible to detect changes of the mechanical operating behavior of bogies without being influenced by effects caused by the road or rails. In an expedient development of the invention, it is possible to measure the external influences of the roadway or rails and thereby determine their condition. The condition of the route can thus be checked with each rail trip. Furthermore, in advantageous developments of the inventive solution, it is also possible to measure the speed and respective position of the vehicle. Thus, the location, time and speed can also be stamped on the individual measurement results, or on the error or alarm messages. In expedient embodiments, the measured speed is utilized as a parameter for evaluating the mechanical operating behavior of the bogie, on one hand, and for precisely determining external influences, on the other hand. In a separate expedient development, external influences caused by the controlling of the vehicle are also taken into consideration.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a device for monitoring the bogies of multi-axle vehicles, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.